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        <td class="header">&nbsp; Orthorectification
            Tutorial
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<h3>Terrain Correction</h3>

<p><font size="-1">The <a href="../operators/RangeDopplerGeocodingOp.html">Terrain Correction</a>
    Operator will
    produce&nbsp;an orthorectified product in the WGS 84 geographic
    coordinates. The&nbsp;Range Doppler
    orthorectification method [1] is implemented for geocoding SAR images from a single 2D
    raster radar geometry. It uses available orbit
    state
    vector information in the metadata or <a href="../operators/ApplyOrbitFileOp.html">external
        precise orbit</a>, the radar timing annotations, the slant to ground range
    conversion parameters together with the reference DEM data to derive the precise
    geolocation information.&nbsp;Optionally radiometric normalisation can be applied to the
    orthorectified image to produce <span style="font-style: italic;">&#963;</span><sup
            style="font-style: italic;">0</sup>, <span style="font-style: italic;">&#947;</span><sup
            style="font-style: italic;">0</sup> or <span style="font-style: italic;">&#946;</span><sup
            style="font-style: italic;">0</sup>
    output.<br></font></p><br>

<p>The <a href="../operators/EllipsoidCorrectionRDOp.html">Ellipsoid Correction RD</a> and
    <a href="../operators/GeolocationGridGeocodingOp.html">Ellipsoid Correction GG</a>
    Operators will&nbsp;produce ellipsoid corrected products in the WGS 84
    geographic coordinates. The Terrain Correction Operator should be used
    whenever DEM is available. The Ellipsoid Correction (RD and GG) should
    be used only when DEM is not available.
</p><h4>Orthorectification Algorithm</h4>

<p>The
    Range Doppler Terrain Correction Operator implements the Range Doppler
    orthorectification method [1] for geocoding SAR images from&nbsp;single 2D
    raster radar geometry. It uses available orbit
    state
    vector information in the metadata or <a href="../operators/ApplyOrbitFileOp.html">external
        precise orbit</a> (only for ERS and ASAR), the radar timing annotations, the slant to ground range
    conversion parameters together with the reference DEM data to derive the precise
    geolocation information.&nbsp;</p><h4>Products Supported</h4>
<ul>
    <li>ASAR (IMS, IMP, IMM, APP, APM, WSM) and ERS products (SLC, IMP) are fully supported.</li>
    <li>RADARSAT-2 (all products)</li>
    <li>TerraSAR-X (SSC only)</li>
    <li>Cosmo-Skymed</li>
</ul>
<h4>DEMs Supported</h4>

<p>Right now only the DEMs with geographic coordinates (P<sub>lat</sub>, P<sub>lon</sub>, P<sub>h</sub>) referred to
    global geodetic ellipsoid reference WGS84 (and height in meters) are properly supported.</p>

<p>STRM v.4 (3&#8221; tiles) from the Joint Research Center
    FTP (xftp.jrc.it) are downloaded automatically for&nbsp; the area covered by the image to be
    orthorectified. The tiles will be downloaded to the folder
    C:\AuxData\DEMs\SRTM_DEM\tiff or the folder specified in the Settings.</p>

<p>The
    Test Connectivity functionality under the Help tab in the main menu bar
    allows the user to verify if the SRTM downloading is working properly. </p>

<p>Please
    note that for ACE and SRTM, the height information (being referred to
    geoid EGM96) is automatically corrected to obtain height relative to
    the WGS84 ellipsoid. For Aster Dem height correction is already
    applied. </p>

<p>Note also that the SRTM DEM covers area between -60
    and 60 degrees latitude. Therefore, for orthorectification of product
    of high latitude area, different DEM should be used. </p>

<p>User can also use external DEM file in Geotiff format which, as specified above, must be with geographic coordinates&nbsp;(P<sub>lat</sub>,
    P<sub>lon</sub>, P<sub>h</sub>) referred to global geodetic ellipsoid reference WGS84 (and height in meters) </p>
<h4>Pixel Spacing</h4>

<p>Besides
    the default suggested pixel spacing computed with parameters in the
    metadata, user can specify output pixel spacing for the orthorectified
    image.</p>

<p> The
    pixel spacing can be entered in both meters and degrees. If the pixel
    spacing in one unit is entered, then &nbsp;the pixel spacing in another
    unit is computed
    automatically.</p>

<p> The calculations of the pixel spacing in meters and in
    degrees&nbsp;are given by the following equations:&nbsp;<span
            style="font-size: 11pt; font-family: &quot;Times New Roman&quot;;" lang="EN-GB"></span><i><span
            style="font-size: 12pt; font-family: &quot;Times New Roman&quot;;" lang="EN-GB"></span></i><span
            style="font-size: 7pt; font-family: Symbol;" lang="EN-GB"></span><i><span
            style="font-size: 12pt; font-family: &quot;Times New Roman&quot;;" lang="EN-GB"></span></i><span
            style="font-size: 7pt; font-family: Symbol;" lang="EN-GB"></span><i><span
            style="font-size: 12pt; font-family: &quot;Times New Roman&quot;;" lang="EN-GB"></span><span
            style="font-size: 8pt; font-family: &quot;Times New Roman&quot;;" lang="EN-GB"></span></i><span
            style="font-size: 12pt; font-family: &quot;Times New Roman&quot;;" lang="EN-GB"></span></p>

<p style="margin-left: 40px;">pixelSpacingInDegree = pixelSpacingInMeter / EquatorialEarthRadius * 180 / PI;</p>

<p style="margin-left: 40px;">pixelSpacingInMeter = pixelSpacingInDegree * PolarEarthRadius&nbsp; * PI / 180;</p>

<p>where&nbsp;EquatorialEarthRadius = 6378137.0 m and PolarEarthRadius = 6356752.314245 m as given in WGS84.&nbsp;</p>
<h4>Radiometric Normalization</h4>

<p>This option implements a radiometric normalization based on the approach proposed by Kellndorfer et al., TGRS, Sept.
    1998 where <br></p>

<div style="text-align: center;"><img style="width: 233px; height: 67px;" alt="" src="images/range_doppler_eq5.jpg">
</div>
<p></p>

<p>In current implementation <span style="font-style: italic;">&#952;</span><sub style="font-style: italic;">DEM</sub>
    is the local incidence angle projected into the range plane and defined
    as the angle between the incoming radiation vector and the projected
    surface normal vector into range plane[2]. The range plane is the plane
    formed by the satellite position, backscattering element position and
    the earth centre.&nbsp;</p>

<p>Note that among&nbsp;<span style="font-style: italic;">&#963;</span><sup
        style="font-style: italic;"><sub>0</sub></sup>, <span style="font-style: italic;">&#947;</span><sup
        style="font-style: italic;"><sub>0</sub></sup> and <span style="font-style: italic;">&#946;</span><sup
        style="font-style: italic;"><sub>0</sub></sup> bands output in the target product, only&nbsp;<span
        style="font-style: italic;">&#963;</span><sup style="font-style: italic;"><sub>0</sub></sup> is real band while
    <span style="font-style: italic;">&#947;</span><sup style="font-style: italic;"><sub>0</sub></sup> and <span
            style="font-style: italic;">&#946;</span><sup style="font-style: italic;"><sub>0</sub></sup> are virtual
    bands expressed in terms of <span style="font-style: italic;">&#963;</span><sup
            style="font-style: italic;"><sub>0</sub></sup>&nbsp;and incidence angle. Therefore, <span
            style="font-style: italic;">&#963;</span><sup style="font-style: italic;"><sub>0</sub></sup>&nbsp;and
    incidence angle are automatically saved and output if <span style="font-style: italic;">&#947;</span><sup
            style="font-style: italic;"><sub>0</sub></sup> or <span style="font-style: italic;">&#946;</span><sup
            style="font-style: italic;"><sub>0</sub></sup> is selected.</p>

<p>For <span style="font-style: italic;">&#963;</span><sup style="font-style: italic;"><sub>0</sub></sup> and <span
        style="font-style: italic;">&#947;</span><sup style="font-style: italic;"><sub>0</sub></sup>&nbsp;calculation,
    by default the projected local incidence angle from DEM [2] (local
    incidence angle projected into range plane) option is selected, but the
    option of incidence angle from ellipsoid correction (incidence angle
    from tie points of the source product) is also available.<br></p><h4>ENVISAT ASAR</h4>

<p>
    The correction factors [3] applied to the original image depend on
    the product being complex or detected and&nbsp;the selection of Auxiliary
    file (ASAR XCA file).&nbsp;</p><h4>Complex Product (IMS, APS)</h4>
<ul>
    <li><span style="font-weight: bold;">Latest AUX File</span>&nbsp;(&amp; use projected local incidence angle computed
        from DEM):<p>The
            most recent ASAR XCA available from the installation folder \auxdata\envisat compatible with product date is
            automatically selected. According to this XCA file, calibration
            constant, range spreading loss and antenna pattern gain are obtained.</p></li>
    <ul>
        <li><span style="text-decoration: underline;">Applied factors</span>:</li>
    </ul>
    <ul>
        <ol>
            <li><p>apply projected local incidence angle into the range plane correction</p></li>
            <li><p>apply calibration constant correction based on the XCA file<br></p></li>
            <li><p>apply range spreading loss correction based on the XCA file and DEM geometry<br></p></li>
            <li><p>apply antenna pattern gain correction based on the XCA file and DEM geometry<br></p></li>
        </ol>
    </ul>
    <li><span style="font-weight: bold;">External AUX File</span>&nbsp;(&amp; use projected local incidence angle
        computed from DEM):<p>User
            can select a specific ASAR XCA file available from the installation
            folder \auxdata\envisat or from another repository. According to
            this selected XCA file, calibration constant, range spreading loss and
            antenna pattern gain are computed.</p></li>
    <ul>
        <li><span style="text-decoration: underline;">Applied factors</span>:</li>
    </ul>
    <ul>
        <ol>
            <li><p>apply projected local incidence angle into the range plane correction</p></li>
            <li><p>apply calibration constant correction based on the selected XCA file<br></p></li>
            <li><p>apply range spreading loss correction based on the selected XCA file and DEM geometry<br></p></li>
            <li><p>apply antenna pattern gain correction based on the selected XCA file and DEM geometry<br></p></li>
        </ol>
    </ul>
</ul>
<h4>Detected Product (IMP, IMM, APP, APM, WSM)</h4>
<ul>
    <li><span style="font-weight: bold;">Latest AUX File</span>&nbsp;(&amp; use projected local incidence angle computed
        from DEM):<p>The
            most recent ASAR XCA available compatible with product date is
            automatically selected. Basically with this option all the correction
            factors applied to the original SAR image based on product XCA file
            used during the focusing, such as antenna pattern gain and range
            spreading loss, are removed first. Then new factors computed according
            to the new ASAR XCA file together with calibration constant and local
            incidence angle correction factors are applied during the radiometric
            normalisation process.</p></li>
    <ul>
        <li><span style="text-decoration: underline;">Applied factors</span>:</li>
    </ul>
    <ul>
        <ol>
            <li><p>remove antenna pattern gain correction based on product XCA file</p></li>
            <li><p>remove range spreading loss correction based on product XCA file<br></p></li>
            <li><p>apply projected local incidence angle into the range plane correction<br></p></li>
            <li><p>apply calibration constant correction based on new XCA file</p></li>
            <li><p>apply range spreading loss correction based on new XCA file and DEM geometry</p></li>
            <li><p>apply new antenna pattern gain correction based on new XCA file and DEM geometry<br></p></li>
        </ol>
    </ul>
    <li><span style="font-weight: bold;">Product AUX File</span>&nbsp;(&amp; use projected local incidence angle
        computed from DEM):<p>The
            product ASAR XCA file employed during the focusing is used. With this
            option the antenna pattern gain and range spreading loss are kept from
            the original product and only the calibration constant and local
            incidence angle correction factors are applied during the radiometric
            normalisation process.</p></li>
    <ul>
        <li><span style="text-decoration: underline;">Applied factors</span>:</li>
    </ul>
    <ul>
        <ol>
            <li><p>apply projected local incidence angle into the range plane correction</p></li>
            <li><p>apply calibration constant correction based on product XCA file<br></p></li>
        </ol>
    </ul>
</ul>
<ul>
    <li><span style="font-weight: bold;">External AUX File</span>&nbsp;(&amp; use projected local incidence angle
        computed from DEM):<p>The
            User
            can select a specific ASAR XCA file available from the installation
            folder \auxdata\envisat or from another repository. Basically with
            this option all the correction factors applied to the original SAR
            image based on product XCA file used during the focusing, such as
            antenna pattern gain and range spreading loss, are removed first. Then
            new factors computed according to the new selected ASAR XCA file
            together with calibration constant and local incidence angle correction
            factors are applied during the radiometric normalisation process.</p></li>
    <ul>
        <li><span style="text-decoration: underline;">Applied factors</span>:</li>
    </ul>
    <ul>
        <ol>
            <li><p>remove antenna pattern gain correction based on product XCA file</p></li>
            <li><p>remove range spreading loss correction based on product XCA file<br></p></li>
            <li><p>apply projected local incidence angle into the range plane correction<br></p></li>
            <li><p>apply calibration constant correction based on new selected XCA file</p></li>
            <li><p>apply range spreading loss correction based on new selected XCA file and DEM geometry</p></li>
            <li><p>apply new antenna pattern gain correction based on new selected XCA file and DEM geometry<br></p>
            </li>
        </ol>
    </ul>
</ul>
<p>
    Please note that if the product has been previously multilooked then
    the radiometric normalization does not correct the antenna pattern and
    range spreading loss and only constant and incidence angle corrections
    are applied. This is because the original antenna pattern and the range
    spreading loss correction cannot be properly removed due to the pixel
    averaging by multilooking. <br></p>

<p>If
    user needs to apply a radiometric normalization, multilook and terrain
    correction to a product, then user graph
    &#8220;RemoveAntPat_Multilook_Orthorectify&#8221; could be used.<br></p><h4>ERS 1&amp;2</h4>

<p>For ERS 1&amp;2 the radiometric normalization cannot be applied directly to original ERS product.<br></p>

<p>Because
    of the Analogue to Digital Converter (ADC) power loss correction , a
    step before is required to properly handle the data. It is necessary to
    employ the Remove Antenna Pattern Operator which performs the following
    operations:</p>

<p>&nbsp;For Single look complex (SLC, IMS) products<br></p>
<ul>
    <li>apply ADC correction</li>
</ul>
<p>For Ground range (PRI, IMP) products:</p>
<ul>
    <li>remove antenna pattern gain</li>
    <li>remove range spreading loss</li>
    <li>apply ADC correction<span style="font-weight: bold;"></span></li>
</ul>
<p>After
    having applied the Remove Antenna Pattern Operator to ERS data, the
    radiometric normalisation can be performed during the Terrain
    Correction.<br></p>

<p>The applied factors in case of "USE projected angle from the DEM" selection are:<br></p>
<ol>
    <li>apply projected local incidence angle into the range plane correction</li>
    <li>apply absolute calibration constant correction</li>
    <li>apply range spreading loss correction based on product metadata and DEM geometry</li>
    <li>apply new antenna pattern gain correction based on product metadata and DEM geometry</li>
</ol>
<p>To apply radiometric normalization and terrain correction for ERS, user can also use one of the following user
    graphs:<br></p>
<ul>
    <li>RemoveAntPat_Orthorectify</li>
    <li>RemoveAntPat_Multilook_Orthorectify</li>
</ul>
<h4>RADARSAT-2</h4>
<ul>
    <li>In
        case of "USE projected angle from the DEM" selection, the radiometric
        normalisation is performed applying the product LUTs and multiplying by
        (sin &#61553;DEM/sin &#61553;el), where &#61553;DEM is projected local incidence angle into
        the range plane and &#61553;el is the incidence angle computed from the tie
        point grid respect to ellipsoid.
    </li>
    <li>In case of selection of "USE
        incidence angle from Ellipsoid", the radiometric normalisation is
        performed applying the product LUT.
    </li>
</ul>
<p>These LUTs allow one to
    convert the digital numbers found in the output product to
    sigma-nought, beta-nought, or gamma-nought values (depending on which
    LUT is used).<br></p><h4>TerraSAR-X</h4>
<ul>
    <li>In case of "USE projected angle from the DEM" selection, the radiometric normalisation is performed applying<br>
        <ol>
            <li>projected local incidence angle into the range plane correction</li>
            <li>absolute calibration constant correction</li>
        </ol>
    </li>
    <li>In case of " USE incidence angle from Ellipsoid " selection, the radiometric normalisation is performed applying<br>
        <ol>
            <li>projected local incidence angle into the range plane correction</li>
            <li>absolute calibration constant correction</li>
        </ol>
    </li>
</ul>
Please note that the simplified approach&nbsp; where Noise Equivalent Beta Naught is neglected has been implemented.<br>
<h4>Cosmo-SkyMed</h4>
<ul>
    <li>In case of "USE projected angle from the DEM" selection, the radiometric normalisation is performed deriving
        <span style="font-style: italic;">&#963;</span><sup style="font-style: italic;"><sub>0</sub></sup><sub
                style="font-style: italic;">Ellipsoid</sub> [7] and then multiplying by (sin<span
                style="font-style: italic;">&#952;</span><sub style="font-style: italic;">DEM</sub> /&nbsp;sin<span
                style="font-style: italic;">&#952;</span><sub style="font-style: italic;">el</sub>), where <span
                style="font-style: italic;">&#952;</span><sub style="font-style: italic;">DEM</sub>&nbsp;is the
        projected local incidence angle into the range plane and <span style="font-style: italic;">&#952;</span><sub
                style="font-style: italic;">el</sub>&nbsp;is the incidence angle computed from the tie point grid
        respect to ellipsoid.
    </li>
    <li>In case of selection of "USE incidence angle from Ellipsoid", the radiometric normalisation is performed
        deriving <span style="font-style: italic;">&#963;</span><sup style="font-style: italic;"><sub>0</sub></sup><sub
                style="font-style: italic;">Ellipsoid</sub> [7] <br></li>
</ul>
<span style="text-decoration: underline; font-weight: bold;">Definitions:</span><br>
<ol>
    <li>The
        local incidence angle is defined as the angle between the normal vector
        of the backscattering element (i.e. vector perpendicular to the ground
        surface) and the incoming radiation vector (i.e. vector formed by the
        satellite position and the backscattering element position) [2].
    </li>
    <li>The
        projected local incidence angle from DEM is defined as the angle
        between the incoming radiation vector (as defined above) and the
        projected surface normal vector into range plane. Here range plane is
        the plane formed by the satellite position, backscattering element
        position and the earth centre [2].<br></li>
</ol>
<h4>Steps to Produce Orthorectified Image</h4>
&nbsp;&nbsp;&nbsp;The following steps should be followed to produce an orthorectified image:<br>
<ol>
    <li>From the Geometry menu select Terrain Correction. This will call up the dialog for the <a
            href="../operators/RangeDopplerGeocodingOp.html">Terrain Correction</a>
        Operator (Figure 1).
    </li>
    <li>Select your source bands.</li>
    <li>Select
        the Digital Elevation Model (DEM) to use. You can select 30
        second GETASSE30 or ACE DEMs if they are installed on your
        computer.&nbsp;Preferably, select the SRTM 3 second DEM which has much
        better
        resolution and can be downloaded as need automatically if you
        have an internet connection.&nbsp;Alternatively,
        you could also browse for an External DEM tile.&nbsp;Currently only DEM in Geotiff format with geographic
        coordinates (P<sub>lat</sub>, P<sub>lon</sub>, P<sub>h</sub>) referred to global geodetic ellipsoid reference
        WGS84 (and height in meters)&nbsp;is accepted.
    </li>
    <li>Select the interpolation methods to use for the DEM resampling and the target image resampling.</li>
    <li>Optionally
        select the Pixel Spacing in meters for&nbsp;the orthorectified image. By default the pixel spacing computed from&nbsp;the
        original SAR image is used.&nbsp;For details, the reader is referred to <span style="font-weight: bold;">Pixel Spacing</span>
        section above.
    </li>
    <li>Optionally
        select the Pixel Spacing in degrees for&nbsp;the orthorectified image.
        By default it is computed from the pixel spacing in meters. If any of
        the two pixel spacing is changed, the other one is updated accordingly.&nbsp;For details, the reader is referred
        to <span style="font-weight: bold;">Pixel Spacing</span> section above.
    </li>
    <li>Optionally select Map Projection. The orthorectified image will be
        presented with the user selected map projection. By default the output
        image will be expressed in WGS84 latlong geographic coordinate.
    </li>
    <li>Optionally select to save the DEM as a band and the local incidence angle.</li>
    <li>Optionally select to apply Radiometric Normalizatin to output <span
            style="font-style: italic;">&#963;</span><sup style="font-style: italic;">0</sup>, <span
            style="font-style: italic;">&#947;</span><sup style="font-style: italic;">0</sup> or <span
            style="font-style: italic;">&#946;</span><sup style="font-style: italic;">0</sup> of the orthorectified
        image.&nbsp;</li>
    <li>Press Run to process the data.</li>
</ol>
<p></p><br>

<div style="text-align: center;"><img style="width: 624px; height: 651px;" alt=""
                                      src="images/range_doppler_dlg.JPG"><br><br><span style="font-weight: bold;">Figure 1. Terrain Correction operator dialog box.</span><br>
</div>
<br><br>

<p><br>Below
    are some sample images showing the Terrain Correction result of an ASAR
    IMS product
    ASA_IMS_1PNUPA20081003_092731_000000162072_00351_34473_2366.N1,
    acquired on&nbsp;October 3, 2008,&nbsp;imaging the area around Rome in
    Central Italy. <br></p>

<p> The ASAR IMS image has been multi-looked with 2 Range looks and 10 Azimuth Looks before to be orthorectified.
    <br><br>The
    DEM employed is the SRTM 3 second Version 4 and since the SRTM height
    information is referred to geoid EGM96, not WGS84 ellipsoid, correction
    has been applied to obtain height relative to the WGS84 ellipsoid (this
    is done automatically)<br><br>Figure 2 is in the original SAR geometry after multi-looking 2-10. <br><br>The
    orthorectified image and its radiometric normalised image &#963;0 are shown in Figure 3&nbsp; and Figure 4
    respectively. <br><br>Figures 5 and 6 are a zoom of the figure 3 and 4.<br><br>The radiometric scale is in
    dB/m^2.<br></p>

<div style="text-align: center;"><img style="width: 592px; height: 616px;" alt=""
                                      src="images/IMP_orig.jpg"><br><br><span style="font-weight: bold;">Figure 3. Original SAR Geometry after multi-looking 2-10.</span>&nbsp;
</div>
<br><br>

<div style="text-align: center;"><img style="width: 722px; height: 569px;" alt="" src="images/IMP_amp.jpg">&nbsp;&nbsp;
    &nbsp; &nbsp; &nbsp; &nbsp;&nbsp; &nbsp; &nbsp; &nbsp;<img style="width: 693px; height: 545px;" alt=""
                                                               src="images/IMP_sigma.jpg"><br><br>

    <div style="text-align: left;"><span style="font-weight: bold;">&nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; Figure 3. Orthrectified image. &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp; &nbsp;
&nbsp;Figure 4. Radiometric normalized image.</span><br></div>
</div>
<br><br><br>

<div style="text-align: center;"><img style="width: 739px; height: 489px;" alt="" src="images/IMP_amp_zoom.jpg">&nbsp;&nbsp;
    &nbsp;<img style="width: 739px; height: 490px;" alt="" src="images/IMP_sigma_zoom.jpg"><br><br>

    <div style="text-align: left;"><span style="font-weight: bold;">&nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp;&nbsp;&nbsp; &nbsp; &nbsp; &nbsp;Figure 5. Zoom in of the
orthorectified image. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp;&nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp;&nbsp;Figure 6.&nbsp;</span><sup><span style="font-weight: bold;"></span></sup><span
            style="font-weight: bold;">Zoom in of the radiometric normalized image</span><span
            style="font-weight: bold;"></span><sup><span style="font-weight: bold;"></span></sup><span
            style="font-weight: bold;">. &nbsp;</span></div>
</div>
<br><br>

<p>After
    Terrain Correction your SAR data will be closer to the real world
    geometry and you will be able to overlay layers from other sources
    correctly.</p>

<p style="font-weight: bold;"><i ,j=""> Reference:</i></p>

<p> [1] Small D., Schubert A.,&nbsp;Guide to ASAR Geocoding, RSL-ASAR-GC-AD, Issue 1.0, March 2008</p>

<p>[2]&nbsp;Schreier G., SAR Geocoding: Data and Systems, Wichmann 1993</p>


<p>[3] Rosich B., Meadows P., Absolute calibration of ASAR Level 1 products,
    ESA/ESRIN, ENVI-CLVL-EOPG-TN-03-0010, Issue 1, Rev. 5, October 2004</p>

<p>[4]
    Laur H., Bally P., Meadows P., S�nchez J., Sch�ttler B., Lopinto E.
    &amp; Esteban D., ERS SAR Calibration: Derivation of &#963;0 in ESA ERS SAR
    PRI Products, ESA/ESRIN, ES-TN-RS-PM-HL09, Issue 2, Rev. 5f, November
    2004&nbsp;</p>

<p>[5] RADARSAT-2 PRODUCT FORMAT DEFINITION - RN-RP-51-2713 Issue 1/7: March 14, 2008</p>

<p>[6] Radiometric Calibration of TerraSAR-X data - TSXX-ITD-TN-0049-radiometric_calculations_I1.00.doc, 2008</p>

<p>[7] For further details about Cosmo-SkyMed calibration please contact Cosmo-SkyMed Help Desk at&nbsp;<font
        color="black" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial;" lang="EN-GB"><a
        href="mailto:info.cosmo@e-geos.it" moz-do-not-send="true">info.cosmo@e-geos.it</a></span></font></p>

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